The present invention relates to weatherable multilayer resinous articles and their preparation. More particularly, it relates to multilayer articles comprising a protective block copolyestercarbonate coating, a second layer comprising a polymer comprising carbonate structural units, a substrate, and at least one adhesive tielayer between the second layer and the substrate.
Various resinous articles have a problem of long term color instability. This causes yellowing of the polymer resin, which in some embodiments detracts from its transparency and attractiveness. Loss of gloss can also be an undesirable long term phenomenon.
Yellowing of polymers is often caused by the action of ultraviolet radiation, which is why such yellowing is frequently designated “photoyellowing”. Numerous means for suppressing photoyellowing have been employed and proposed. Many of these involve incorporation in the polymer of ultraviolet absorbing compounds (UVA's). For the most part, UVA's are low molecular weight compounds and they must be employed at relatively low levels, typically up to 1% by weight, to avoid degradation of the physical properties of the polymer such as impact strength and high temperature properties as reflected in heat distortion temperature. Such levels may be inadequate to afford sufficient protection.
One way of protecting a resinous article against photoyellowing and loss of gloss is to apply a coating of a weatherable second polymer, the term “weatherable” as used herein signifying resistance to such phenomena. Weatherable polymers suitable for this purpose include resorcinol isophthalate/terephthalate copolyarylates. This is the subject of Cohen et al., J. Poly. Sci., Part A-1, vol. 9, pp. 3263–3299 (1971), and certain related U.S. Patents of Monsanto Company including U.S. Pat. Nos. 3,444,129, 3,460,961, 3,492,261 and 3,503,779. Commonly owned, published application WO 00-61664 is directed to weatherable multilayer articles with coating layers comprising structural units derived from a 1,3-dihydroxybenzene organodicarboxylate. Commonly owned U.S. Pat. No. 6,306,507 is directed to weatherable multilayer articles with coating layers comprising at least one coating layer thereon, said coating layer comprising a thermally stable polymer comprising resorcinol arylate polyester chain members substantially free of anhydride linkages linking at least two mers of the polymer chain, prepared by an interfacial method.
Japanese Kokai 1/199,841 discloses articles having a substrate layer comprising at least 90 mole percent poly(ethylene terephthalate) and a gas barrier coating layer which is a polyester of resorcinol and isophthalic acid, optionally with copolyester units derived from another dicarboxylic acid such as terephthalic acid, naphthalenedicarboxylic acid or various other specifically named dicarboxylic acids. The disclosed articles may be prepared by a series of operations including co-injection molding which are essentially performed entirely in the melt, thereby overcoming the aforementioned deficiencies of solution coating. However, the only types of articles disclosed are bottles, which are produced from a co-injection molded parison by subsequent blow molding. Larger articles intended for outdoor use, such as external automobile body parts, are not disclosed and no method for their production is suggested, nor are articles in which the substrate layer is anything other than poly(ethylene terephthalate).
It remains of interest, therefore, to develop a method for preparing weatherable multilayer articles which are capable of use for such varied purposes as body parts for outdoor vehicles and devices such as automobiles, and which exhibit adequate adhesion between the various layers.